The number of US deaths from the novel coronavirus rose to six on Monday, all in the state of Washington, officials said, signalling the contagion has taken root in the Pacific Northwest.

Vice President Mike Pence announced a treatment for the disease could be available by summer or early fall, but that a vaccine was farther off.

Five of the six American fatalities have been from King county, the most populous in Washington state and home to Seattle, a city of more than 700,000 people. The sixth victim was from neighboring Snohomish county, officials said.

“Although most of the cases will be mild or moderate, the infection can cause serious illness and there’s a potential for many people to become ill at the same time.” The state reported four new cases, three from the same nursing home, taking the total number of US cases to more than 90 about half of which were people repatriated from either China or a virus-stricken cruise ship off Japan.

Dow Constantine, the top official in King County, said his office was in talks to purchase a motel in which to place people who required isolation, adding: “We have to move to a new stage in the fight to contain, mitigate and manage this outbreak.” Pence told reporters at the White House that treatments “could literally be available by this summer, or early fall.” He was likely referring to the drug remdesivir, an antiviral drug developed by the pharmaceutical firm Gilead that has already been used to treat one US patient and was moving toward two final stage expansive clinical trials in Asia.

New travel protocols “will ensure that anyone traveling on a direct flight to the United States of America receives multiple screenings at all airports in Italy and South Korea,” he said.

“The estimates that we’re getting from industry right now, by the end of this week close to a million tests will be able to be performed,” said Food and Drug Administration chief Stephen Hahn.

In New York, Governor Andrew Cuomo warned it was “inevitable” that the virus would spread in the global financial hub after its first confirmed case was detected in a health care worker who had visited Iran.